There have been conventionally proposed various kinds of grinding mills such as a ball grinding mill, a vibration grinding mill, a roller grinding mill, a jet grinding mill, and the like. In case of the jet grinding mill, especially, it could reach the fineness of the material to be finely ground into a size of a range of 5 μm. However, there haven't been proposed any grinding mill having the result with the fineness in a range between 0.1 μm and 1 μm in a dried manner. By the way, this has been achieved depending upon the wet grinding manner that has some disadvantages of producing waste water, raising process costs, making the process complicated, and causing the components of the material to be ground to be varied.
Only in case of special works, thus, nano-sized particles that are produced in the wet grinding manner, at the expense of substantially high manufacturing costs, have been used, and even though the excellence of the nano-sized particles is noticed, the use of the particles is being limited because of their high production costs.